1. Field of the Invention
The invention relates to a microscopy system for eye surgery to support a surgeon performing a surgical eye treatment, and the invention relates to a method of illuminating the eye under surgery.
In particular the microscopy system is configured to provide an appropriate illumination for a treatment of a region of the eye, such as a cornea, an iris, and a lens of the eye. A possible application of the microscopy system is a cataract surgery, where a natural lens of the human eye, in which a cataract has developed, is to be substituted by an artificial lens.
2. Brief Description of Related Art
In the following a conventional microscopy system for eye surgery is explained with reference to FIGS. 1 to 3:
FIG. 1 schematically illustrates a beam path of a microscopy system 1. The microscopy system 1 comprises an objective lens 3 with an optical axis 5 and an object plane 7, in which a region of the eye under surgery is arranged. The objective lens 3 transforms a beam 11 on an object side and emerging from the object plane 7 into an angle 9 about the optical axis 5 to infinity, and transforms the beam 11 to a beam 13 on the image side.
In the beam 13 on the image side, two zoom systems 15, 16, each having an optical axis 17 and 18, respectively, are arranged adjacent to each other such that their optical axes 17, 18 are displaced in parallel to the optical axis 5 of the objective lens 3 and arranged with a distance a from each other. Each of the zoom systems 15, 16 receives a partial beam 19 and 20, respectively, of the beam 13. The partial beam 19 is supplied to a left eye 21 of the surgeon, and the other partial beam 20 is supplied to the right eye 22 of the surgeon. A lens 23 of a tube, a prism system 25 and an ocular 27 are arranged in the beam path of the partial beams 19, 20. The left eye 21 perceives the object plane 7 inclined by a perspective angle α with respect to the optical axis 5. The right eye 22 perceives the object plane 7 inclined by a perspective angle −α with respect to the optical axis 5. Thereby, the surgeon obtains a stereoscopic impression of the region of the eye under surgery and arranged in the object plane 7.
For example, for removing the natural lens during a cataract operation it is necessary to remove the lens completely by sucking it off. It turned out that remaining portions of the lens of the eye are well visible to the surgeon when a retroillumination is employed which is sometimes also referred to as a red reflex illumination. Herein, light is emitted from an objective lens 3 side of the microscope through the pupil 32 (see FIG. 2) and through the lens 33 of the eye into an inside of the eye 31, and the light is incident on the retina 34 and the eye fundus, respectively. There the irradiated light is reflected and illuminates the lens 33 of the eye and the remaining portions of the lens from the backside, thus facilitating their visibility. Herein, the retina reflects substantially only red light, so that the lens 33 of the eye or its remaining portions appear in a red light, from which the designation red reflex illumination is derived.
FIGS. 2 and 3 show an arrangement of a retroillumination device 35 used for generating the red reflex.
The top view of FIG. 3 shows the zoom systems 15, 16 and centers 36 of beams 20 entering the zoom systems at a plane of an objective lens 3. In addition, FIG. 3 shows a connecting line 38 between the centers 36 in a plane of the objective lens 3. This connecting line 38 is arranged with a distance from the optical axis 5 such that in the side view according to FIG. 2, main rays of the partial beams 19, 20 extend under an angle δ with respect to the optical axis which may also be zero.
Light of a light source, not shown in FIG. 2, is supplied by an illumination system 35 via an optical fiber 37; the light is expanded by a collimation optic 39 and formed to a parallel beam 40. A mirror 41 is arranged with a distance from the optical axis 5 of the objective lens 3 and directs a partial beam of the beam 40 generated by the collimation optic 39 such that this partial beam extends in parallel to the optical axis 5 of the objective lens 3 and traverses the objective lens 3. Thus, as seen in the side view of FIG. 2, a main ray of the partial beam enters the eye 31 under an angle β of about 2° with respect to main rays of the observation beams 19, 20 as a beam of retroillumination light 43; and, as indicated in FIG. 2 by the arrows 34, the partial beam is reflected there and generates the retroillumination and the red reflex, respectively. The angle β=2°, specified above, is exemplary. Other angles as those between −2° and +2° have proven favorable.
In addition to the beam of retroillumination light 43, a main ray of a beam of standard illumination light 45 is incident on the object plane 7 under a greater angle ε of about 7° to the plane of main rays of the observation beams 19, 20. A mirror 47 generates the beam of standard illumination light 45 by redirecting the light beam 40, provided by the collimation optic 39. The beam of standard illumination light serves as the usual illumination of the object plane 7 and herewith of the region of the eye 31, at which the treatment is carried out. The beam of standard illumination light 45 illuminates those regions of the eye which are arranged in the object plane 7, such as the iris, such that these regions may be well perceived by the surgeon. The beam of standard illumination light does substantially not contribute to generation of the red reflex. The beam of standard illumination light 45 serves for the illumination of the object plane with an illumination light well facilitating the usual visual observation, without contributing substantially to the generation of a red reflex; in particular the illumination light lets the objects, which are arranged in the object plane, appear in true colors. The mirror 47 comprises a cutout 49 for light penetration to the mirror 41.
In practice, generating the red reflex and maintaining the red reflex during the surgical treatment, especially when the eye is moving, or the lens is changed, is often involving a considerable effort. Further attention has to be paid that for protection of the retina of the eye an intensity of the retroillumination has to be limited so that the red reflex cannot always be generated with the desired intensity.